Spectacular Wyoming Supercell
Most all tornadoes form out of Supercell thunderstorms. However not all supercell thunderstorms produce tornadoes. A spectacular example of a non-tornadic supercell occurred May 18 2014 in eastern Wyoming. While hail as large as softballs were reported with the storm, there were no tornado sightings.
Storm Chaser Colt Forney captured an amazing video of this supercell